[TMS]

I thought I would share for those wondering just how far you can push the LT4 with the factory stock cam on Ethanol before running out of fuel headroom. So began my quest to push as close to E-85 as safely as possible.

Here was my setup at testing:
Stock 1.7L LT4 blower and drive pulley
9.17" lower crank pulley (15% OD) (peak boost about 14 psi)
91 octane mix with E-85
Stock lowside pump
Stock highside pump and injectors

All log tests were done in 3rd gear, 1500 rpm to about 5,500 rpm rolling WOT digs.

As was predicted, my lowside fueling ran out first. I was pushing my way up and got to E-50 when the lowside tanked. Fuel pressure dropped below 50 psi and pulsewidth went to 9.3ms - yikes! So first order of business was to address the lowside. Tuner (Ted Jannetty) recommended a JMS FuelMax booster. I wired that in and repeated the test with E-50. This time the low side held strong with a steady pressure of about 73-74 psi. It did not waver. The highside though was just starting to dip at about 4,000 RPM and then recovered. Pulsewidth was still a bit high at 6.7ms at this dip.

At this point, without more fueling mods on the highside, this was about max I could go, and to get below 6ms I need to run E-45.

Not wanting to yet do a cam to address the high side, I thought I would swap the high-side pump and injectors for Lingenfelter's products. So new LPE pump and injectors went in. Once the tuning was refined, I began pushing up the Ethanol to see how far we could get.

I started at E-78. The highside dropped way low and the pulsewidth was at a steady 9.5ms between 3200 rpm and 4,000 rpm and then begins recovering just a bit. What is really interesting here is that the lowside fuel pressure never wavered. It stayed flat at 73-74 psi.

I began diluting my ethanol with 91 gasoline and got down to E-66. On E-66, my lowside was steady as commanded as expected and the highside was dipping at 4,000 rpm and then recovering. Very similar to E-50 before the pump/injector upgrades. Highest pulsewidth reached 6.0ms.

I run E-60 as a max which keeps my pulsewidths below 5.0ms.

My conclusion is that with the addition of the LPE pump and injectors, I can run E-60 safely. Before upgrades I could run E-45 safely. This is good for a 15% increase. Although, had I not had other upgrade plans for the car I would have never spent the money on the injectors (maybe the pump) as this is an expensive proposition to squeeze out an extra 15% ethanol.

I think the biggest surprise was that the JMS booster continued to hold up the lowside fueling demands. I thought for sure we would have seen a dip on the lowside running E-78. At least for my setup, I don't think I'll need to do anything further with the lowside fueling. At least not until the new weak link (high side fuel headroom) is remedied. I'm a big, big advocate for the JMS booster after going through this. It will move the fueling weak link elsewhere and keep it there for quite some time.

For those not wanting to break into the engine to cam it, this thread may be helpful. While I can't say for sure, it seems likely that at stock boost levels, I likely could run full E-85. Maybe I'll test that out.